Process for preparing cyclopropyl alkyl ketones and 4,5-dihydroalkyfurans

Abstract

The invention relates to a novel process for simultaneously preparing cyclopropyl alkyl ketones and 4,5-dihydroalkylfurans from 3-acyltetrahydrofuran-2-ones in the presence of a metal salt according to the scheme ##STR1## during the reaction, high-boiling poly (ethylene glycol) dialkyl ethers are then used. By introducing the solvent, the metal salt and the 3-acyltetrahydrofuran-2-one in a molar excess to the metal salt, heating the mixture to 160° to 220° C. and adding further 3-acyltetrahydrofuran-2-one, the desired products are obtained in high yields. The metal salt can, moreover, be recovered in a simple manner by washing with water.

What is claimed as new and desired to be secured by Letters Patent of the United States is: 
     
       1. A process for simultaneously preparing cyclopropyl alkyl ketones of the formula I and alkyl-4,5-dihydro-2-alkylfurans of the formula II from 3-acyltetrahydrofuran-2-ones of the formula III ##STR4## where R 1  =C 1-4  alkyl, cyclohexyl or phenyl and R 2  =H, C 1-4  alkyl or phenyl, comprising   reacting a metal salt and 3-acyltetrahydrofuran-2-one III, in a molar excess to the metal salt, in a solvent comprising a poly(ethylene glycol) dialkyl ether of the formula IV ##STR5## where R 3 , R 4  are each independently C 1-4  alkyl   R 5  =H or methyl and   n=20 to 50, heating the mixture to 160° to 220° C., then adding further 3-acyltetrahydrofuran-2-one of the formula III and distilling off cyclopropyl alkyl ketone of formula I and alkyl-4,5-dihydro-2-alkylfuran of formula II in the course of this.   
     
     
       2. The process of claim 1, wherein said metal salt used is an alkali metal halide. 
     
     
       3. The process of claim 2, wherein said metal salt is selected from the group consisting of NaI, KI and a mixture thereof. 
     
     
       4. The process of claim 1, wherein said metal salt and III are introduced in a molar ratio of 1:2 to 1:10. 
     
     
       5. The process of claim 1, said metal salt and 3-acyltetrahydrofuran-2-ones of the formula III are introduced in a molar ratio of 1:2.5 to 1:5. 
     
     
       6. The process of claim 1, further comprising recovering said metal salt by washing with water, after the distillation of cyclopropyl alkyl ketone of formula I and alkyl-4,5-dihydro-2-alkylfuran of formula II. 
     
     
       7. The process of claim 1, wherein said solvent IV further comprises up to 50% by weight of a high-boiling, polar, water-soluble solvent, based on the total amount of solvent. 
     
     
       8. The method of claim 1, wherein said 3-aceytetrahydrofuran-2-one of formula III is selected from the group consisting of α-acetyl-γ-butyrolactone, 3-acetyl-5-methyltetrahydrofuran-2-one, α-benzoyl-γ-butyrolactone, α-acetyl-α-phenyl-γ-butyrolactone and α-benzoyl-α-methyl-γ-butyrolactone. 
     
     
       9. The method of claim 1, wherein said cyclopropyl alkyl ketoneof formula I is selected from the group consisting of cyclopropyl methyl ketone, cyclopropyl ethyl ketone, cyclopropyl phenyl ketone, cyclopropyl cyclohexyl ketone and 1-methylcyclopropyl phenyl ketone. 
     
     
       10. The method of claim 1, wherein said 4,5-dihydroalkylfuran of formula II is selected from the group consisting of 4,5-dihydro-2-methylfuran, 4,5-dihydro-2,5-dimethylfuran, 4,5-dihydro-2-phenylfuran, 4,5-dihydro-2-cyclohexylfuran and 4,5-dihydro-5-methyl-2-phenylfuran. 
     
     
       11. The method of claim 1, wherein said poly(ethylene glycol)dialkyl ether of formula IV is selected from the group consisting of poly(ethylene glycol) dimethyl ether, poly(ethylene glycol) diethyl ether, poly(propylene glycol) dimethyl ether and a mixture thereof. 
     
     
       12. The method of claim 1, wherein said metal salt is selected from the group consisting of alkali metal halides, alkaline earth metal halides and a mixture thereof. 
     
     
       13. The method of claim 1, wherein said metal salt is selected from the group consisting of LiBr, LiI, KCl, NaBr, KBr, NaI, KI and a mixture thereof. 
     
     
       14. The method of claim 1, wherein a concentration f of said metal salt is 5 to 20% by weight based on said mixture of solvent and 3-acyltetrahydrofuran-2-one of formula III. 
     
     
       15. The method of claim 1, wherein heating said mixture is from 180° to 200° C. 
     
     
       16. The method of claim 7, wherein said high-boiling, polar, water-soluble solvent is selected from the group consisting of dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone and a mixture thereof.